Energy consumption in the telecommunication industry has direct impact on the total energy consumption of the world. For example, in 2005, the Telecom Italia network consumed over 2 TWh, which is about 1% of all Italian energy consumption. Energy consumption also implies the generation of CO2 gas, e.g., 2 TWh is equivalent to 4,000,000 ton of CO2 emission. Therefore, it is therefore important to reduce energy consumption of telecom networks.
Next generation Optical Transport Network (OTN) frames transport data using Optical Data Units (ODUs). Different level of the ODUs can carry traffic at different data rate. Specifically, ODU0 carries 1.25 Gbps, ODU1 carries 2.5 Gbps, ODU2 carries 10 Gbps, ODU3 carries 40 Gbps, and ODU4 carries 100 Gbps (all values are nominal).
It is known that the processing of larger ODUs at a cross connect (XC) consumes half the energy per bit than smaller ODUs. Consequently, an optical path with large amount of data consumes less energy per bit than paths with smaller ODUs.
Each optical fiber can carry optical data traffic over multiple wavelengths. A typical core optical network can have line rates of 10, 40 or 100 Gbps. This means that each wavelength can carry information at 10, 40 or 100 Gbps. For example, if a wavelength has 100 Gbps, the fiber can be used to carry a single ODU4, or 4 ODU3, or any other combinations of ODU of different levels. When the wavelength carries more than one ODU, the optical signal is converted to electrical signal at the XC. Data of each ODU are processed at the XC, and then converted back to the optical domain before transmitted by a corresponding output port.
When the wavelength carries only a single ODU, and the data are routed to the same wavelength at an output port of the XC, an optical bypass can be used. An optical bypass does not require optical-to-electrical (O2E) and electrical-to-optical (E2O) conversion, (herein after “conversions”), thus the bypass consumes substantially less energy than any other switching scheme requiring conversion.